1. Technical Field
This disclosure relates generally to hydraulic systems and, more specifically, to return or inlet lines to a hydraulic tank or reservoir that are equipped with diffusers. The diffusers are used to control the delivery of high velocity hydraulic fluid that is returned to the tank.
2. Description of the Related Art
Fixed and/or variable positive displacement hydraulic pumps have numerous applications in many fields, including automotive, aerospace, industrial, agricultural, heavy equipment and the like for performing work. In a typical hydraulic system, return fluid is simply returned into the pump reservoir where it dwells for time period before being drawn in by the inlet to the pump for recirculation. Under conditions of high load and high flow rate, such hydraulic systems may be unable to keep up with the fluid demand of the pump, leading to cavitation and unacceptable levels of noise. Another inherent disadvantage with such systems is that the kinetic energy of the incoming fluid to the reservoir is lost and not utilized to feed the inlet to the pump, leading to relatively low efficiencies.
Specifically, hydraulic fluid or oil in such a system is moving at a high velocity when it is returned to the tank. The high velocity flow rates result in considerable amounts of turbulence. The turbulence has many undesirable effects, such as causing cavitation in the hydraulic circuit. Another undesirable effect is that the turbulence causes fluid to be lost through the reservoir air vent. This results in permanent loss of the fluid and causes the fluid to coat the exterior of the equipment, creating safety and cleanliness problems.
In the past, hydraulic tanks have been provided with baffles and the direction of discharge has been varied in an attempt to correct the above problems. However, baffles are not preferable because they consume space in the tank and limit the design possibilities for the tank. More recently, the inlet lines to hydraulic tanks had been equipped with a diffuser for reducing the velocity and turbulence of the hydraulic fluid being returned to the tank. The use of a diffuser may also eliminate the need for one or more baffles.
The use of a diffuser for hydraulic high-speed return lines to slow down the fluid entering the tank is shown, for example, in U.S. Pat. No. 4,127,143, which discloses a frustoconically shaped diffuser having an internal diameter that expands as it enters the tank. However, the '143 patent also relies upon a baffle between the tank inlet and the outlet. Many currently available diffusers are essentially screen-like axial extensions to the inlet and the screen may deaerate the fluid as well as reduce the velocity of the fluid thereby reducing turbulence and foaming. Currently available diffusers may also trap particles that are present in the returning fluid which may help protect the downstream components, such as the pump.
However, currently available return diffusers for hydraulic tanks are subject to damage when the pressure of the returning fluid spikes. This problem is particularly prevalent in high velocity/high-pressure applications. Therefore, there is a need for improved return lines and diffusers for hydraulic tanks that effectively reduce the velocity of the returning fluid, deaerate the fluid, reduce the turbulence and foaming of the fluid as well as remove particulate matter from the fluid, but which are less prone to damage resulting from fluid flow or pressure spikes.